Cancer will continue to be a primary cause of death for the foreseeable future, but early detection of tumors would improve patient prognosis (R. T. Greenlee et al., Cancer statistics, 2000, CA Cancer J. Clin., 2000, 50, pp. 7–33). Despite significant advances in current methods for the diagnosis of cancer, physicians still rely on the presence of a palpable tumor mass. At this, however, the many benefits of early medical intervention may have been already compromised.
Photodiagnosis and/or phototherapy has a great potential to improve management of cancer patient (D. A. Benaron and D. K. Stevenson, Optical time-of-flight and absorbance imaging of biologic media, Science, 1993, 259, pp. 1463–1466; R. F. Potter (Series Editor), Medical optical tomography: functional imaging and monitoring, SPIE Optical Engineering Press, Bellingham, 1993; G. J. Tearney et al., In vivo endoscopic optical biopsy with optical coherence tomography, Science, 1997, 276, pp. 2037–2039; B. J. Tromberg et al., Non-invasive measurements of breast tissue optical properties using frequency-domain photon migration, Phil. Trans. Royal Society London B, 1997, 352, pp. 661–668; S. Fantini et al., Assessment of the size, position, and optical properties of breast tumors in vivo by non-invasive optical methods, Appl. Opt., 1998, 37, pp. 1982–1989; A. Pelegrin et al., Photoimmunodiagnosis with antibody-fluorescein conjugates: in vitro and in vivo preclinical studies, J. Cell Pharmacol., 1992, 3, pp. 141–145). These procedures use visible or near infrared light to induce the desired effect. Both optical detection and phototherapy have been demonstrated to be safe and effective in clinical settings and biomedical research (B. C. Wilson, Optical properties of tissues, Encyclopedia of Human Biology, 1991, 5, 587–597; Y-L. He et al., Measurement of blood volume using indocyanine green measured with pulse-spectrometry: Its reproducibility and reliability, Critical Care Medicine, 1998, 26, pp. 1446–1451; J. Caesar et al., The use of Indocyanine green in the measurement of hepatic blood flow and as a test of hepatic function, Clin. Sci., 1961, 21, pp. 43–57; R. B. Mujumdar et al., Cyanine dye labeling reagents: Sulfoindocyanine succinimidyl esters, Bioconjugate Chemistry, 1993, 4, pp. 105–111; U.S. Pat. No. 5,453,505; Eric Hohenschuh, et al., Light imaging contrast agents, WO 98/48846; Jonathan Turner, et al., Optical diagnostic agents for the diagnosis of neurodegenerative diseases by means of near infra-red radiation, WO 98/22146; Kai Licha, et al., In-vivo diagnostic process by near infrared radiation, WO 96/17628; Robert A. Snow, et al., Compounds, WO 98/48838].
Dyes are important to enhance signal detection and/or photosensitizing of tissues in optical imaging and phototherapy. Previous studies have shown that certain dyes can localize in tumors and serve as a powerful probe for the detection and treatment of small cancers (D. A. Bellnier et al., Murine pharmacokinetics and antitumor efficacy of the photodynamic sensitizer 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a, J. Photochem. Photobiol., 1993, 20, pp. 55–61; G. A. Wagnieres et al., In vivo fluorescence spectroscopy and imaging for oncological applications, Photochem. Photobiol., 1998, 68, pp. 603–632; J. S. Reynolds et al., Imaging of spontaneous canine mammary tumors using fluorescent contrast agents, Photochem. Photobiol., 1999, 70, pp. 87–94). However, these dyes do not localize preferentially in malignant tissues.
Efforts have been made to improve the specificity of dyes to malignant tissues by conjugating dyes to large biomolecules (A. Pelegrin, et al., Photoimmunodiagnosis with antibody-fluorescein conjugates: in vitro and in vivo preclinical studies, J. Cell Pharmacol., 1992, 3, pp. 141–145; B. Ballou et al., Tumor labeling in vivo using cyanine-conjugated monoclonal antibodies, Cancer Immunol. Immunother., 1995, 41, pp. 257–263; R. Weissleder et al., In vivo imaging of tumors with protease-activated near-infrared fluorescent probes, Nature Biotech., 1999, 17, pp. 375–378; K. Licha et al., New contrast agents for optical imaging: Acid-cleavable conjugates of cyanine dyes with biomolecules, Proc. SPIE, 1999, 3600, pp. 29–35). Developing a dye that can combine the roles of tumor-seeking, diagnostic, and therapeutic functions has been very difficult for several reasons. The dyes currently in use localize in tumors by a non-specific mechanism that usually relies on the lipophilicity of the dye to penetrate the lipid membrane of the cell. These lipophilic dyes require several hours or days to clear from normal tissues, and low tumor-to-normal tissue ratios are usually encountered. Furthermore, combining photodynamic properties with fluorescence emission needed for the imaging of deep tissues requires a molecule that must compromise either the photosensitive effect of the dye or the fluorescence quantum yield. Photosensitivity of phototherapy agents relies on the transfer of energy from the excited state of the agent to surrounding molecules or tissues, while fluorescence emission demands that the excitation energy be emitted in the form of light (T. J. Dougherty et al., Photoradiation therapy II: Cure of animal tumors with hematoporphyrin and light, Journal of National Cancer Institute, 1978, 55, pp. 115–121). Therefore, compounds and compositions that have optimal tumor-targeting ability to provide a highly efficient photosensitive agent for treatment of tumors are needed. Such agents would exhibit enhanced specificity for tumors and would also have excellent photophysical properties for optical detection.
Each of the references previously disclosed is expressly incorporated by reference herein in its entirety.